Hello, i have the deco x50 v1.33 and i'm having problems with it

1 - My 2.4Ghz speed in the first connection hits 50mbps, after 3 minutes decreases to 10mbps, even closer to the router, my internet speed is 420mb of download. I already tried to optimize network and say its ok. Tried deactivate 5Ghz, tried guest network and iot and still the same. Others routers with 2.4GHz hits 100mbps with no problem. Someone has a solution for this problem? The 5Ghz speed still good. This affect some cameras that need the video be sended to a cloud to return to me.

2 - Some cameras looses connection too, i put prefered connection, deactivate the mesh connection, put high priority and the cameras access only the iot network with 2.4GHz. But i'm still facing the problems

I bought more 2 deco s7 but i will return to the seller for this problems, unfortunately I can no longer return this deco x50, i need a solution.

Deco x50 v1.33 - 1.2.10